1. Field of the Invention
The present invention relates to inverter capacitor modules and inverters, and more particularly, the present invention relates to an inverter capacitor module and an inverter for use, for example, in a power module or other suitable apparatus.
2. Description of the Related Art
Inverters are provided with switching elements and capacitors. As shown in FIG. 6, a terminal 52 of a capacitor 51 is electrically connected to a switching element 53. Although only the terminal 52 is shown in FIG. 6, other terminals of the capacitor 51 having different polarities are each electrically connected to the switching element 53. In an actual inverter, the capacitor 51 and the switching element 53 are mounted on an insulating housing (not shown).
As has been demanded for other electrical devices and electrical components, miniaturization has been demanded for inverters as well. In Japanese Unexamined Patent Publication No. 9-308265, there is disclosed an inverter device for an electric vehicle for achieving an effective utilization of installation space by decreasing the installation area.
In this inverter device, a smoothing capacitor including an electrolytic capacitor is provided above a switching module by bending an input conductive plate connected to an input terminal unit of the switching module and then by connecting the smoothing capacitor to the bent input conductive plate. Since the smoothing capacitor having the relatively bulky electrolytic capacitor is disposed above the switching module, reduction in the installation area can be achieved.
Since, as described above, the conventional inverter makes use of the bulky electrolytic capacitor, an electrical connection member located between the capacitor and the switching module, such as the input conductive plate, requires a certain length. Hence, an inductance component occurs in this electrical connection member.
In order to decrease the inductance component, the capacitor should be located nearer to the switching module. Therefore, the capacitor has been arranged so as to be as close to the switching module as possible.
However, the electrolytic capacitor is bulky, requiring a certain length for the electrical connection member between the electrolytic capacitor and the switching module. Therefore, as long as the electrical connection member has a certain length, there are limits to minimizing the inductance component.
Furthermore, since the conventional inverter is provided with the bulky electrolytic capacitor, the size of the inverter cannot be reduced. In addition, since sufficient heat dissipation cannot be provided, resin must be filled in a casing in order to increase the amount of heat dissipation.
To solve these problems, a flat-type capacitor module obtained by mounting a plurality of ceramic capacitors having first and second terminals in a substrate and the inverter provided with this capacitor module are proposed in Japanese Unexamined Patent Application No. 11-361548 (not published). However, when the capacitance is insufficient, the substrate size of the capacitor module must be increased in order to increase the number of mounted ceramic capacitors. Accordingly, when the switching module is mounted below the capacitor module, the downwardly projected area of the capacitor module is larger than the area of the switching module. This makes it difficult to miniaturize the inverter.
In order to overcome the problems described above, preferred embodiments of the present invention provide an inverter capacitor module and an inverter that is miniaturized, has excellent dissipation characteristics and that minimizes an inductance component generated in an electrical connection member located between a capacitor module.
In addition, preferred embodiments of the present invention provide an inverter capacitor module and an inverter that are miniaturized even when a larger capacitance is provided therein.
According to a first preferred embodiment of the present invention, an inverter capacitor module includes a plurality of substrates having a plurality of ceramic capacitors provided on the top surfaces thereof, and first and second feeding unit lands having conductive films disposed on both surfaces thereof for feeding the plurality of ceramic capacitors, the first and second feeding unit lands on both surfaces thereof being electrically connected to each other, a conductive spacer inserted between the plurality of substrates for establishing one of an electrical connection between the first feeding unit lands of an underlying substrate and its overlying substrate and an electrical connection between the second feeding unit lands of an underlying substrate and its overlying substrate, a fixing device arranged to fix the plurality of substrates laminated via the conductive spacer, and a switching module arranged so as to be fixed below the bottom substrate among the plurality of substrates that are laminated. In the inverter capacitor module, the switching module is fixed to the plurality of substrates by the fixing device.
In the inverter capacitance module, the fixing device fixes a plurality of substrates provided with a plurality of ceramic capacitors in a laminated arrangement via the conductive spacers, so that the conductive spacers establish electrical connections between the substrates. Therefore, the capacitance can be easily adjusted by increasing the number of substrates instead of increasing the downwardly projected area of the capacitor module. Since the switching module is fixedly mounted on the bottom surface of the bottom layer substrate, when the inverter is constructed using the capacitor module and the switching module in the above-described fixed manner, the area required to install the inverter is greatly decreased.
Alternatively, in the inverter capacitor module, a plurality of ceramic capacitors each includes first and second terminals. The first terminal is electrically connected to the first feeding unit land and the second terminal is electrically connected to the second feeding unit land.
Since each of the ceramic capacitors which includes the first and second terminals have the first and second terminals electrically connected to the first and second feeding unit lands, respectively, each substrate can be connected to a plurality of laminated capacitors in parallel.
Alternatively, in the inverter capacitor module, a plurality of substrates each includes a printed-circuit board and first and second through-hole electrodes arranged to establish electrical connections between the first feeding unit lands on both surfaces of each of the plurality of substrates and between the second feeding unit lands on both surfaces of each of the plurality of substrates, respectively.
When the through-hole electrodes each establish the electrical connections between the first feeding unit lands and between the second feeding unit lands provided on both surfaces of each of the substrates including the printed-circuit boards, the circuit provided in each of the substrates can be connected in parallel via the conductive spacers.
Alternatively, in the inverter capacitor module, a projecting unit upwardly projecting from the top surface or downwardly projecting from the bottom surface of the conductive spacer and including a male screw disposed on the outer periphery of the projecting unit is provided, a hole including a female thread capable of being engaged with the male screw in the inner periphery of the hole is provided in the bottom surface or the top surface of the conductive spacer, and a plurality of conductive spacers is fastened using the male screw and the female screw provided in the hole.
When the projecting unit having the male screw disposed on the outer periphery thereof is provided on the top surface or the bottom surface of the conductive spacer and the screw hole having the female thread disposed on the internal periphery thereof is provided on the bottom surface or the top surface of the conductive space, a plurality of conductive spacers can be fastened using the male screws and the screw holes of the conductive spacers. That is, since the male screw and the screw hole constitute the fixing device, another fixing member such as a bolt is not required. In addition, since the fastening force is independently applied to each substrate, the contact resistance between the substrate and the conductive spacer can be decreased and can be stabilized. In addition, since the electrical connection can be achieved via the contact device between the male screw and the screw hole, the current amount is increased and the heat is eliminated.
According to another preferred embodiment of the present invention, an inverter includes the inverter capacitor module according to the above-described preferred embodiment of the present invention and a switching module mounted on the bottom surface of the bottom layer substrate of the capacitor module.
Since the inverter includes the above-described inverter capacitor module and the switching module mounted below the bottom layer substrate of the capacitor module, a miniaturized inverter that easily varies the capacitance is easily provided.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached figures.